In the world that we live in today, safety and environmental issues are of paramount importance. During filling operations of tanks, vessels, fill lines, hoses, pipelines or tubulars for transportation of fluids that are harmful to personnel or the environment, it is necessary to use a valve which precludes spillage when the hose or transportation device is disconnected from the structure being filled. These valves must also allow fluid to flow in the reverse direction to prevent over pressuring. For these reasons, these types of valves are generally referred to as fluid safety valves or pressure relieving valves.
In one application the filling and or circulation operations of tubulars (OCTG) used primarily for the drilling and completing of oil and gas or geothermal wells, where it is necessary to run or pull tubulars (OCTG) into or out of a wellbore. When running tubulars into or out of the wellbore, it is common to fill each joint with drilling or wellbore fluid (also known as drilling mud). The drilling or wellbore fluid is a mixture of various chemicals required to support varying operations or conditions which often contain elements of a high viscous nature. When introduced to valves or restrictions, the drilling or wellbore fluid can be highly corrosive or abrasive especially when transported or delivered under pressure. A valve is normally installed below the Kelly or top drive to prevent the discharge of the drilling or wellbore fluid from spilling onto the rig floor where it is a hazard to personnel and the environment. These valves allow drilling or wellbore fluid to flow into the tubular (OCTG) while pumping but will automatically close when pumping is discontinued. These types of valves are known as “Standing or Mud Saver Valves”. There are numerous prior art patents for these types of valves. These prior art designs generally include a closure member, an abutting seat member, and a means for urging the closure member toward the seat. The prior art also tended to have no matched flow capability in opposing directions, bi-directional reverse flow capability, and a restricted or reduced flow through bore and could only be used in a vertical application.
Each of the prior art valves disclose many advantages and enhancements in safety and or valve designs. However, each of the valves has certain shortcomings. The main shortcoming being the lack of a matched full flow through the valve cavity, pressure balancing, bi-directional capability and no restrictions on plane of operation.
A second shortcoming is the lack of wear resistance. Many drilling or wellbore fluids, especially those used in drilling applications, contain elements of a high viscous nature and high solids content. These solids can be sand, barite, and a variety of other chemical materials used to create higher density fluids. These types of fluids can be very abrasive and therefore erosive. Prior art designs contain sharp edges, irregular or nonlinear flow paths, small cross sectional flow areas, or all of the aforementioned, causing turbulence within the valve. The combination of these factors leads to premature wear and ultimately failure.
A third disadvantage to prior art designs is that the seat is held rigid as it is encountered by the closure member when the valve closes. This rigidity can cause a violent impact between the closure member and the seat. These impacts cause severe wear to the sealing surfaces leading to a possible catastrophic failure of the valve.
A fourth disadvantage to prior art designs is the closure member does not have a mechanical means to limit its axial movement. This creates two problems. First, the spring urging the closure member towards the abutting seat can be compressed further than the spring manufacturer's recommended deflection, overstressing the spring, causing it to fail. Secondly, the lack of a limiting means causes chattering of the closure member against the seat, thereby causing premature failure wear. This is due to the pump pressure forces being constantly resisted by the spring. As the pump pressure fluctuates, the closure member correspondingly moves closer to and away from the seat. When the pump pressures and or flow rates are such that these fluctuations occur while the closure member is very close to the seat, chattering occurs. This chattering effect is detrimental to the sealing surfaces and can lead to catastrophic failure of the valve.
A fifth disadvantage to prior art designs is the lack of ability to have a full flow capability in reverse flow or the cross sectional area for reverse flow is very small. These restricted fluid flow passages increase the amount of time necessary to relieve the pressure built up or trapped and again lead to catastrophic failure of the valve, tank or containment vessel.
A sixth disadvantage to prior art designs is the absence of a means to adjust to pressures or flow rates at which the valve opens in both directions. Many valves use a ball type check for reverse flow that relies on gravity to hold it firmly against its seat. This provides no means of adjusting the pressure at which the check opens. It also will not function in orientation other than vertical.
A seventh disadvantage to prior art designs is the chamber or cross sectional space housing the closure member spring is not sealed from the fluids being circulated. The circulation of fluids laden with sand or other solids can cause build up of these solids around the coils of the spring. This can reduce the deflection of the spring causing the flow area between the closure element and the seat to become restricted. This build up can also completely eliminate the spring deflection blocking all flow through the valve and can lead to potential catastrophic failure of the valve or associated equipment.